<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <title><box-sizing></box-sizing></title>
    <meta name="viewport" content="width=device-width, initial-scale=1">
</head>
    <style>
        ul{
            list-style:none;
            overflow:hidden;
            width: 100%;
        }
        * {
            margin :0;
            padding: 0;
        }
        li {
            width:200px;
            height:200px;
            line-height:200px;
            padding: 10px;
            text-align:center;
            float: left;
            border: 20px solid black;
            box-sizing: border-box;
        }
    </style>
<body>
    <ul>
        <li>1</li>
        <li>2</li>
        <li>3</li>
        <li>4</li>
        <li>5</li>
    </ul>
</body>
</html>